i feel you in every heartbeat
by UnlessIt'sEvil
Summary: The AU in which, on their 22nd birthday, a person will switch bodies with their soulmate and is left to figure out whom they're temporarily inhabiting, and how to get back to each other. But because Stiles is Stiles, he forgets that it's his birthday, and the bodyswap takes him by surprise. / Sterek, one-shot, rated T, guest appearance by Laura Hale.


**i feel you in every heartbeat**

_Did you know that writing bodyswap kissing is really awkward? Especially when all your knowledge on kissing in general is from fanfiction in the first place._

_Yeah._

_This fic was written for a prompt sent to me by my main girl Leni, and it has taken me almost two months, because I had no clue how to even tackle the whole bodyswap concept. Writing normal, single-body-inhabitation fics is already hard enough most times._

_**i.**_

He'd had it all planned out.

He made the decision when he was eleven, when they started teaching them about it at school. The day of his twenty-second birthday, and therefore of one other specific person's twenty-second year of living, he would take a day off from whatever responsibility he had—be it school or work or playing video games with Scott or, hell, he'd even give up tagging along with his dad to an epic murder scene—and he'd go to his dad's house well on time, and he'd lay down in his bed and just wait. He'd wait for the clock to turn twelve-oh-three in the afternoon, for what others described as a tingly feeling spreading up from his toes to his head. Then, he would feel like he was floating, and the next instant he would be in somebody else's body. And someone else would be in his.

He would swap bodies with his soulmate.

Of course, it was always possible that his soulmate had died, or that there had been a problem during their birth and therefore the swapping process would get messed up; it only worked if both parties were born at the exact same time, on the exact same day. He wasn't going to think about that, though he didhave a plan in case that happened—ways to seek out this person, track down hospital records and such. Danny would crack from his groveling eventually.

Yes, Stiles had a plan.

Then finals happened.

Stiles _knew _he shouldn't have taken those twelve-week courses instead of the normal sixteen-week ones. But he'd done it anyway with the thought that it would mean more time off between semesters. So in the rush of studying, extra caffeine shots, trying to convince Scott that starting a relationship so close to his twenty-second birthday was a bad idea, and juggling his job with all of the above, he had completely forgotten that it was his own birthday.

He didn't really pay it any mind when his toes started going numb during his Trig 1 exam. He was merely annoyed when the numb, slightly ticklish feeling spread up to his calves. He was silently asking the universe what he'd done to deserve this treatment when his thighs started twitching minutely. Reaching down with the hand not holding his pen, he rubbed his leg while looking over the next problem on his test. Part of his attention went out to the equations, while the other part of his ADD brain was supplying him with ways to describe the sensations now going up to his hips. Numb, heavy, itchy, sparkly, twitchy, tingly—

Tingly. He was feeling tingly. It was 12:03 PM on the eighth of April and there was a tingly feeling spreading up from his toes.

It was as if the realization had sped up the process, because suddenly his entire body felt tingly and sensitive and he could swear gravity had failed on him just then; he couldn't feel the chair he was sitting on, or where he'd planted his feet on the floor, or the clothes he was wearing, or the pen he was holding, and then his vision started blurring and morphing into a picture of some place that was _not_ his classroom.

"Oh, shi—"

"—it," he finished with a different voice. He sat up in a flash, gripping his head with foreign hands a moment later at the wooziness that resulted. Groaning in that voice, which—damn, it sounded nice, and distinctly male—he took stock of himself and his surroundings.

He was clearly no longer 140 pounds of fragile skin and bones, because he was definitely having trouble getting up from—what, a bed? Yes, a bed. He was in his soulmate's bed, because his soulmate had remembered to be considerate about the whole thing and prepare for the soulswapping. As opposed to Stiles, who had forgotten and left his soulmate to the fate of disorientation in the middle of a full classroom. Well, this relationship was already up to a good start.

And wow, arms. Maybe it was just the angle, but whomever's body Stiles was in was packing some serious muscles. And, oh, that was a very flat stomach under a very tight grey t-shirt.

Experimentally, Stiles lifted a (fucking _giant_) hand to his torso and, yeah. Abs. Lots of them. And thighs. And—he shifted a bit in his seat—testicle game strong. Stiles had won the fucking jackpot, he knew, and he hadn't even seen the guy's _face_ yet. There was a mirror in the corner of the room, though, so he set out to change that fact.

The room he was in was pleasant, light and airy. It looked like a teenager's bedroom, except more tidy than any teenager would keep it. Probably where his soulmate slept before leaving to college, which he clearly had; only mothers would keep a room this clean. He could see some sports trophies here and there. (Baseball and _lacrosse_, Stiles noted as Common Interest #1 on his mental checklist of Shit To Talk About With My Soulmate.) And shit, the bed was comfy. Stiles looked forward to defiling it in the hopefully near future. If, you know, his soulmate would ever forgive him for being such a dick and forgetting their birthday. Dammit.

It was more than odd to walk on legs not his own, but he got over it soon enough and made a beeline for the mirror, only to promptly get all the oxygen sucked out of his foreign lungs, and probably straight from his bloodstream and fucking _brain_ because _holy fucking shit fuck—_

The person staring back at him in the mirror was _Derek fucking Hale._

Derek, a friend of Boyd's up in Berkeley and therefore tentative acquaintance of Stiles. Derek, who was probably the single most gorgeous person to walk this earth, and Stiles had gone to high school with Lydia Martin and Danny Mahealani, for God's sake. Derek, who aside from his good looks was really fucking intelligent and had all the same opinions and tastes and passions as Stiles, except _more_ because Derek was better at everything, including just being himself.

Derek, who hated Stiles' guts.

Stiles wanted to whine, to cry a bit at the circumstances, but was certain that Derek would find out if Stiles cried big fat girly tears in Derek's body, and probably skin Stiles' body in revenge. With Stiles back in it, of course.

And God, Derek was perfect. Men weren't supposed to be described as beautiful, according to society, but the description fit. And oh, what sweet torture it was, to know that Stiles' soulmate was this ethereal-looking being, but Stiles _still_ didn't stand a chance.

Something had to have gone wrong, with either Stiles' birth or Derek's, because there was no way the universe had decided _them_ as compatible partners. Derek would never go for someone like Stiles, couldn't even tolerate him whenever they were in a room together. Whenever they all gathered together—Stiles, Derek, Boyd, Erica, Isaac, and the occasional visiting Scott—Derek did everything he possibly could to stay on the far end of their group, the other side of where Stiles would be standing or sitting. Derek wouldn't even _look_ at Stiles, that's how much he disliked him.

Stiles was still staring in horrified fascination at his own expression in Derek's chiseled face, when the bedroom door burst open. Stiles flailed, which really didn't work quite as well with Derek's arms, and spun around to face a tall woman with Derek's hair and eyes. She was just as heartbreakingly stunning, and Stiles mentally cursed his fate some more.

She grinned widely, wolfishly, and Stiles was kind of scared of her. "Hi! Hi, nice to meet you, I'm Laura, the sister of the person you're currently inhabiting," she said, holding out her hand for Stiles to shake. He took it after some awkward aiming—Derek's hands were significantly bigger than Stiles'—and said, "Hey, ah, there's been a mistake."

Laura abruptly stilled their hands, which had been swinging up and down wildly, and narrowed her eyes. "What, don't like what you see?"

He snorted, and then winced when Laura's hand tightened on his. She was surprisingly strong for someone shorter and skinnier than his borrowed body. "No, no, are you kidding me? Derek's gorgeous, I just—"

"Wait, did you just say Derek?" Laura's hand paused the crushing of his, and she stared at him, perplexed. "I never told you his name. You've already met?"

Stiles sighed, letting not-his chin drop down onto not-his very chiseled chest. "Yeah, yeah we do. And Derek is probably throwing a fit right now because he's stuck inside of me."

"Oh," she whispered, dropping his hand at last. The cut off blood flowed into it painfully, and it felt like a metaphor for Stiles' life right then. Laura shifted from foot to foot for a few moments, before finally speaking. "He called me a week ago, upset, because he's fallen for someone. I guess you know that then, right? That he's already in love? It's why he was so nervous for today. There was a big chance he wouldn't be paired with them." Her voice broke when she said love, and he could hear the pity plain and clear.

He slowly moved his gaze from the floor up to her face. "I didn't even know that, I just knew he didn't like me at all. Hates me, actually. I don't even know what I did to offend him."

He couldn't really read the look on Laura's face in reaction to that, and in his melancholy didn't bother trying to.

_**ii.**_

Apparently, Laura inherited the Hale family's house when her and Derek's parents died. She lived here with her own mate, who was currently away at work. Their other siblings, of which there were many, had all moved out by this point, either in a home with their own significant others or away at college. Said siblings, as well as uncles and aunts and cousins and Derek himself, came over during holidays or between semesters, and all stayed in the house during these times. It was certainly big enough for that amount of people. Big and light and cozy, and Stiles could see why they all wanted to get together here several times per year.

Down in the kitchen, Laura fed him, and made him explain the situation while he was eating his grilled cheese sandwich.

"So let me get this straight, Derek, who you claim hates you, ended up inside of you—" "You make it sound so _dirty._" "—while you were doing a math final? Really? That's so rude, Stiles."

"I forgot!" he exclaimed, spraying chewed up bits of melted cheese all over the counter, which earned him a scolding face from Laura. "Have you been to college? Do you know how stressful finals are? Especially since this is my last semester before getting my Master's."

She raised one perfectly shaped eyebrow at him. "Well yeah, finals got me in a funk too, but I made sure to plan _around_ my twenty-second birthday. As did Derek, who, as you know, goes to Berkeley as well."

Stiles groaned. "Yes, I _know,_ I get it, I'm really stupid. God, Derek's going to hate me even more now."

Laura put a comforting hand on not-his shoulder. "I'm sure he doesn't really _hate_ you. He's just weary to let anyone close, especially if he likes them, because what if they're his mate? He can't establish a certain type of relationship with anyone, platonic or otherwise, and risk having it all turned over because of the whole soulmate shebang."

Stiles scrunches up not-his nose at that. "Why can't he just ask everyone around him when they were born? That should clear it all up. And _yes, _I know," he says at the look Laura sends him. "It's like an unspoken agreement in today's society that it's rude to inquire, and that knowing who your soulmate is beforehand can get in the way of living life to its fullest, blah-blah-blah. But _not_ asking and therefore not letting anyone get close to you _also_ gets in the way of living life to its fullest! Seriously, the norms surrounding the whole soulmate situation are bullshit.

The corner of Laura's mouth twitches, and he can almost feel the amusement in the air between them. "I guess you've thought a lot about this?"

Stiles sighs. "Yeah, when I was younger, I had this giant crush on a now good friend of mine, Lydia. It went on all the way into my senior year. I was so sure she was my soulmate, but because of these unwritten rules we have, I couldn't ask about her birthday. So I went through years of hoping, of having this dream occupy my every day, only to find out she's actually a year younger and was only in my class because she's, like, stupidly smart. See, if I'd known this beforehand, I would have never let myself get lost in this fantasy of me and Lydia building a life together, and I would have focused more on school, maybe even gotten into Harvard like she did."

The amused tilt to her lips dropped and she looked almost defeated. "Shit, you haven't really had much luck in the whole love department, have you? You mistook someone for your soulmate, and now you're getting your heart crushed by the actual one."

"Yeah, thanks for summing it up for me," he said a bit bitterly. Next thing he knew, Laura was walking around the counter and throwing her arms around him in an awkward sideways hug, not-his bicep wedged between her breasts and her head nuzzling in the space between not-his shoulder and neck.

"I think you're seeing this more negatively than required," she whispered into not-his skin. "You and Derek are soulmates, there's no way you can't get over the situation that's been keeping you apart."

"The situation being him already being in love?"

"At least you know he's capable of love," she said wryly. He couldn't argue with that.

_**iii.**_

He walked out onto the Hale's front porch with the goal of getting into Laura's car with her and driving to Berkeley to face Derek's Stiles-wearing wrath, but he froze when he saw it.

They were surrounded by woods. With trees he knew. And shrubbery he knew. And he was facing a driveway that he most definitely recognized.

Walking out onto said driveway, he turned to face the front of the house and proceeded to curse in a manner that would put angry sailors to shame, because God dammit, he _knew this house._

"We're in Beacon Hills!" he yelled, possibly more loudly than necessary and scaring a few birds into flying off their perches in the trees.

Laura, who had been in the process of locking the front door, gaped at him. "You know Beacon Hills?"

He waved his arms in no particular direction. "I'm _from_ Beacon Hills! My dad's the Sheriff!"

Laura dropped her facy leather handpurse. "_You're_ the Sheriff's kid? _Stilinski?!_" she screamed just as loudly, and the birds that had returned flew away once more. She mirrored his frantic gesturing and then paused. "Wait, your name is Stiles Stilinski? Really?"

"It's a nickname," he grumbled. "But that's not what's important—I've trick-or-treated here. I've been here before; I'd just never been inside. Holy shit," he rubbed not-his hand over not-his face. "I've probably even met Derek before, you as well!"

She made the 'mind-blown' gesture, putting her fists at either side of her head and then unfurling them as she dropped her hands, puffing out air and widening her eyes. "What even," she said, and Stiles knew he would miss her a lot when he and Derek inevitably decided to ignore their soulmatedness in favor of looking for a partner the alternative way.

"But wait," he said when the realization hit him. "Derek wasn't in any of my classes."

"We were home-schooled," Laura told him. Which actually explained a lot, such as why he didn't recognize Derek, or Laura for that matter, from the get-go.

Stiles was about to say as much, when a buzzing sound came from the purse still lying on the porch. Laura bent to retrieve her phone, and frowned. "Unknown number," she said, and then gasped, "What if it's Derek using your phone? Do you recognize this number?"

She hurried to show him the screen, and yeah, that was in fact his number. He told her such and she quickly picked up. "Derek? Oh my God, I can't believe we didn't think of calling Stiles' phone earlier," she said into it, and Stiles agreed. He figured they'd been too preoccupied with Stiles-pining-after-Derek-pining-after-someone-else dilemma.

Stiles could feel not-his heart speeding up as he heard his own voice over the phone, tinny and too faint to make out words. Laura's face turned an alarming shade of read in response to whatever Derek was saying, and her facial twitches were downright fascinating.

"Are you saying what I think you're saying?" she said into the phone slowly, almost cautiously, and Derek's borrowed voice seemed louder this time when he spoke. Whatever was being said made Laura slap her hand over her mouth, and her eyes were comically wide. Stiles would have been muffling laughter at this point, were it not for the nerves and adrenaline going through not-his system.

She turned to face Stiles in the eyes, and he wasn't entirely sure what she was trying to convey with her look. Derek finished speaking then, and she removed her trembling—trembling!—hand from her mouth. She was still red in the face.

"Okay, yeah, no, we'll come get you. We're already out by the car—" Derek interrupted her. "Oh, okay, uh, yeah, if that's what you want." She seemed hesitant to say that, and Stiles was dreading whatever Derek had said to make her react that way. They said their goodbyes, and Stiles was faintly aware he was breathing faster than normal.

"Right, so, Derek said I should come pick him up at Berkeley and bring him here. Alone. And for you to wait here for our return."

Stiles didn't know how to answer for a few seconds. It didn't seem like a good thing that Derek didn't want to see him to come. "All right," he finally said, because what else was there to say?

Laura sent him another one of her pitying glances, and patted him on the back. "It'll all be fine, Stiles, don't worry. Trust me on this one, okay? I'll see you soon." And then she was in the car, and driving away, and Stiles just kind of stood there in front of the Hale house for a solid half hour before going inside to wait and wallow there.

_**iv.**_

The caffeine-high Stiles had achieved back in his own body had apparently transferred into this one, because when that excess energy dwindled down, he crashed and fell asleep with his head on his arms on the kitchen counter. He was still fighting his way into the waking world when he heard tires rolling on gravel, and the significance of the sound didn't really hit him until the door suddenly opened and the gust of wind made him jump up.

Looking at himself from someone else's perspective was probably even weirder than being in said perspective in the first place. Hearing his own voice from someone else's ears was quite the odd experience as well.

"Stiles?" Derek said with Stiles' voice.

"Yeah," he said. "Hi, yes, hi, Derek. Um, so, I'm really sorry about the whole classroom thi—mph."

Derek was kissing him. Derek in Stiles' body was kissing Stiles in Derek's body, Stiles' hands being controlled by Derek on Derek's face being worn by Stiles. Stiles was basically kissing himself, except he wasn't because it was Derek in there.

Which, yeah. That was kind of the important bit; _Derek was kissing him._

He was too dumbstruck to respond before Derek pulled back, and the look on his—Stiles'—face was downright _scared._ Scared and undoubtedly hopeful.

"Laura told me, told me that she told you that I told her, and before you decide anything I need to tell you that what I told her was about _you,_" Derek said.

Stiles blinked. "Come again?"

Derek looked to be steeling himself, before putting his lips on Stiles' once more, gentler this time, barely a faint touch of mouths before pulling back again. He stayed much closer this time, though, and said, "The reason I've been cold towards you, distant, is because I was afraid. As soon as Boyd introduced us, as soon as I saw you I was gone, Stiles, I was just gone on you but I knew it was a risk to develop serious feelings for you, because what if someone else was supposed to be my soulmate? What if your birthday came before mine and I would have to be there through you finding love, while I was there, waiting for my own? When I called Laura to tell her that I had fallen for someone, I was talking about you, Stiles. Because no matter how much I avoided you, when we ran into each other all you'd have to do was _smile_ and I'd know it was a lost cause." He took a deep breath, leaning his forehead up against Stiles' and softly rubbing their noses together. It was downright adorable, and Stiles wanted to just kind of drip down onto the floor into a melted puddle of goop. Death by swooning. His dad would have to arrest Derek for killing Stiles with his wooing skills and utter cuteness.

He realized after a while that Derek was probably waiting for an answer, and Stiles just kind of made this sound in the back of not-his throat and pulled Derek's borrowed face down to not-his own and repeated what Derek had done earlier.

Derek responded almost immediately, and deepened the kiss. The strangeness of technically kissing himself was overshadowed by the tongue he could feel on not-his lips and just when he finally remembered how to move not-his jaw in order to open not-his mouth and allow not-Derek's tongue entrance, they heard someone clearing their throat right next to them.

Stiles pulled away to look at an exasperated-looking Laura, and tried to ignore how Derek was still staring at him intently as Laura said, "Not that I'm not heart warmed by this display of affection, but really, I'm still present, and I'd appreciate if you'd hold your horses until you can actually find a room. And no, you are _not_ to just run up to Derek's room, because this house is way too noisy for comfort—"

Derek completely disregarded her words and instead took ahold of not-Stiles' hand and pulled him up the stares, Laura's indignant protests becoming background noise as they got lost in wandering hands and whispered confessions.

They didn't do anything other than kissing, silently agreeing that doing anything more when not in their own bodies was way too weird for either of them. Instead, they made out for a while and joined Laura for dinner that evening. That night, they fell asleep on top of each other, whispering confessions and clearing up some final details.

The next day, they were lazing on Derek's old bed, crammed against each other because it was technically too small for two people. Derek had made banana pancakes for Stiles as a late breakfast, and Stiles was absently rubbing his contently full belly when the tingling feeling swept up from his toes to his head much faster than the previous day, and he heard Derek suck in a breath as he went through the same.

And _bam_, he was suddenly on the other side of the bed, and when he turned his head, he was looking at Derek, and it was actually _Derek_, as in tall-muscly-stubbly Derek, and he couldn't help but laugh.

Derek was grinning widely, and _damn_ did he look good happy. "Hey," Derek said, and the fondness was evident. Stiles had thought for so long that he'd never get this, that he'd never even get to see Derek _smile_. Now, he had it, and shit, it felt good.

And Stiles' earlier wish of defiling Derek's childhood bedroom? It came true.

Pun very much intended.

**the end**

_Comments are always appreciated! Anything to improve my writing._

_My twitter username is kiraswolf, and my tumblr is hillsofbeacon._


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